Study of aerodynamic characteristics of variable cross-section box girders under three-dimensional fluctuating wind...

The irregular aerodynamic shape of a variable-section box girder leads to an obvious disturbance in the surrounding flow field, and the fluctuating wind will further change the spatial flow characteristics of the flow field. Therefore, it is crucial to explore the aerodynamic characteristics of a variable-section box girder when subjected to fluctuating wind conditions, as well as the flow characteristics of the surrounding airflow. Based on the advantages of numerical simulation for convenient control of fluctuating wind characteristics, this paper presents a three-dimensional large eddy simulation (3D-LES) of a variable-section box girder, and five wind fields with different fluctuating characteristics are simulated by the method of Narrow-band Synthetic Random Flow Generation (NSRFG). A comparative analysis is performed to evaluate the influence of fluctuating wind on the wind pressure coefficients, aerodynamic force coefficients, and spanwise correlation of aerodynamic forces of the box girder at different angles of attack. Additionally, the changes in the flow field around the main girder are examined using power spectral density. The findings indicate that, in comparison to the average wind field, only the near windward end of the upper and lower surfaces in the fluctuating wind field increases in negative pressure, and the rest of the field shows a tendency to weaken negative pressure. The drag and lift coefficients have a maximum reduction of 13.67% and 34.18%, respectively, in the fluctuating wind field, but the torque coefficient of a small depth-width ratio section shows a maximum increase of 21.43%. Turbulent flow distortion enhances the box girder aerodynamic spreading correlation in the fluctuating wind field, as compared to the average wind field. The power spectral density response of fluctuating wind only changes the intensity of vortex shedding but does not affect the frequency of vortex shedding.